Passenger service units of the aforementioned type are known in the state of the art and are widely used in civil aircrafts. Generally a passenger service unit comprises a reading light, a passenger air supply device, oxygen masks, warning lights and the like appliances. In some aircrafts one passenger service unit is provided for each seat of a passenger and crew member. In other aircrafts one single passenger service unit is provided for a number of the seats, e.g. in particular for a row of seats. A row usually is aligned crosswise to an alley of seats; a row may have two, three, four, five, six or more seats depending on the size of the civil aircraft. Modern civil aircrafts cabins may have a capacity of several hundred seats for passengers.
Emergency situations on board of an aircraft may be characterized by a decompression of the cabin, smoke or fire, wind turbulences and mechanical impacts or the like. Generally an emergency situation is to be understood any kind of situation wherein a use of an oxygen mask is advisable in an aircraft. Usually, a pilot will seek to conduct a quick emergency descent of the aircraft in such an emergency situation and to reach the closest airport or emergency landing lane. However, a descent of the aircraft may require more time than estimated. However, also after landing the aircraft, a quick exit of all passengers out of the aircraft may be required. Such quick exit may be hindered by smoke and/or insufficient oxygen in the aircraft passenger cabin.
It is known to supply oxygen to passengers in an emergency situation like a situation mentioned above, in particular a decompression situation and/or a situation accompanied by development of smoke or fire in the cabin. Especially for these kinds of situation, oxygen masks drop out of a passenger service unit and oxygen is supplied to the passenger via said oxygen mask. Usually the oxygen mask is connected to the passenger service unit via a connecting line. In the passenger service unit a common oxygen source is comprised which stores oxygen and provides said oxygen to the passenger after activation of the oxygen supply, preferably to a plurality of emergency oxygen supply masks. Usually, the passenger can activate the oxygen supply pulling a connecting line wherein said connecting line may be a flexible tube which at the same time serves to direct the oxygen from the passenger service unit to the oxygen mask or maybe a wire or rope or the like distinct from the connecting line.
It is known to store oxygen in the passenger service unit in a chemically bound form and to produce said oxygen in a chemical reaction after activation. This type of oxygen source is called chemical oxygen generator (COG).
It is further known to store oxygen in a pressurized tank wherein activation of said oxygen source comprises opening a valve or a sealing component to open said pressure tank and allow flow of oxygen out of said tank to the oxygen mask. It is known to provide an emergency oxygen supply mask of this known kind with a re-breather-bag or concentrator or the like to improve an oxygen supply to the passenger.
In particular for a pilot or a crew member of an aircraft it is known to provide On-Board Oxygen System (OBOGS) units have been used. Such OBOGS units use a microcellular sieve to filter the nitrogen out of the air to supply oxygen enriched breathable air. They are able to literally “produce its own oxygen” by means of depleting ambient air. It is possible to produce output gases which are enriched up to 95% percent of oxygen. Such an OBOGS unit is known to supply oxygen to pilots of a military aircraft.
Nevertheless such kind emergency oxygen devices have shown to be insufficient in certain emergency situations, in particular in case of smoke or fire in the cabin or during the quick exit of the passengers out of the cabin or in situations wherein estimated amount of oxygen available from a common oxygen source runs to a limit.